OK. I can see possibilities but none quite seem to match. <any />
looks like it might come closest (with some changes), but still looks
like it is going to perform (at least) one SELECT for every <meta-
value /> it encounters. <dynamic-component /> also seems very close,
but would require me to use an IDictionary to store values (where the
keys map to column names within the one table), rather than to store
strongly-typed classes that access the values (where the classes are
persisted to their own tables). I also assume that <dynamic-
component /> will try to return all values defined in the mapping, not
specific ones.
Note that I'm not trying to retrieve sets of data where the properties
can be different per row, but I am trying to retrieve sets where the
properties could be different per set.
Allowing me to return, fleetingly, to pseudo-code examples (note the /
psuedo/ aspect here), I am after a means to specify what I want to
return, have NHibernate generate the SQL to do so and populate the
component objects for me.
(new CompObj()).GetByID(1) returns:
SELECT id
FROM comp_objs
WHERE oid = 1
(new CompObj(new Positional())).GetByID(1) returns:
SELECT id, x, y
FROM comp_objs t1
LEFT JOIN pos_objs t2 ON t1.oid = t2.oid
WHERE t1.oid = 1
(new CompObj(new Positional(), new Colored())).GetByID(1) returns:
SELECT id, x, y, r, g, b
FROM comp_objs t1
LEFT JOIN pos_objs t2 ON t1.oid = t2.oid
LEFT JOIN col_objs t3 ON t1.oid = t3.oid
WHERE t1.oid = 1
This does not seem unrealistic to me. Is such generation/mapping
possible within NHibernate?
On Aug 3, 2:56 am, Diego Mijelshon <[email protected]> wrote:
> NH can support most models based on sane inheritance and composition.
> It's hard to tell which parts are requirements and which are just
> implementation ideas... but you can definitely map a CompositeObject which
> has a set or map of inherited CompositeObjects, for example.
>
> Diego
>
> On Mon, Aug 2, 2010 at 22:38, jimbobmcgee <[email protected]>wrote:
>
> > I appreciate that it may look like I'm asking a lot but I'm not asking
> > as much as you might first think; it's just a little tough for me to
> > conceptualise without some rudamentary example of what I am trying to
> > achieve (hence the extensive code snippets). I've got the
> > architecture and design down (at least conceptually), now I'm looking
> > to see how I might leverage NHibernate given that concept.
>
> > Now, let me see if I can distill the concept/question into something
> > wih a couple less paragraphs:
>
> > Given an outer POCO object, with a collection member, where each item
> > of the collection is a different inner POCO object (i.e. stored in
> > different tables) that has a one-to-one relationship with the outer
> > POCO (enforced by foreign primary keys), is there a way to configure
> > NHibernate either so that it understands the join or that it will
> > generate the SQL to query it, without the specific content of the
> > collection member being known at design time?
>
> > (Now, to me the above question seems harder to understand than that
> > with the examples...)
>
> > Your answer, 'probably not', is most likely the correct one, in which
> > case NHibernate would not be suited for my specific needs. That's no
> > biggie, it just means I won't be able to use it. I'm not trying to
> > shoehorn in NHibernate where it will not fit, merely evaluating it
> > considering my needs. If it were a specific issue I was addressing,
> > I'm sure I could RTFM; the documentation is hardly incomplete and
> > there are a wealth of articles out there covering many basic mapping
> > issues. But having spent a couple of evenings Googling and not being
> > able to break the question down into terse, boolean logic, I thought
> > I'd try a higher form of human language interpretation.
>
> > (And, of course, if I were required to use NHibernate and required to
> > use composite objects, I would consider consulting hours from an
> > expert NH developer; but for a proof-of-concept piece, not likely).
>
> > On Aug 3, 1:32 am, Diego Mijelshon <[email protected]> wrote:
> > > On Mon, Aug 2, 2010 at 19:03, jimbobmcgee <[email protected]
> > >wrote:
>
> > > > A colleague of mine has been trying to convince me to use NHibernate
> > > > in an upcoming project ...
>
> > > > [...unhelpful critique...]
>
> > > > Semantics aside, do you think this is something NHibernate could help
> > > > me achieve? If so, what do you think would be the most elegant way to
> > > > do it?
>
> > > Yes... No... Maybe.
> > > Probably not.
>
> > > In any case (leaving acid humor aside for a second) you are asking for
> > > architecture, design, guidance, and implementation all at once in a
> > single
> > > email.
> > > We can help you with specific issues ("does NH support composite keys?"
> > "how
> > > do I eagerly load two collections?", "how would you map this inheritance
> > > structure?")
> > > If you need more than that, you should buy some consulting hours from any
> > of
> > > the expert NH developers around here.
>
> > > Diego
>
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